Process and device for the electrolytic surface coating of workpieces

Abstract

A process and apparatus for electrolytically surface-coating special metal workpieces in which the electrolyte is conveyed in a controlled circuit in and around the electrolysis region in that most of it is conveyed at a high flow rate, at a higher inlet pressure, through the space between a cathodically connected workpiece and an anode and a smaller proportion of it is conveyed at a lower flow rate upwards to the rear of the anode away from the cathode. After leaving the electrolysis region the electrolyte is taken into a separate overflow tank and/or in the feed back system. The device for implementing said process is an electrolysis tank, inlet lines or apertures for the electrolyte at the base of the chamber between the cathodically connected workpiece and the anode or below and behind the anode, at least one overflow tank connected on or beneath the electrolysis container into which the electrolyte is fed after passing through the electrolysis region and a feed back device for the electrolyte with a filter.

Claims

1. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into an fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into an electrolysis tank and into and around an electrolysis region in the electrolysis tank, the electrolysis region being defined by an anode and a cathodically connected workpiece, the electrolysis tank having an overflow region through which electrolyte can flow from the electrolysis region and into an overflow tank, the anode having a first side closest to the workpiece and a second side farthest from the workpiece, a greater portion of the electrolyte being conveyed in a first stream from a first inlet at a higher flow rate into a space between the cathodically connected workpiece and the anode, the first stream flowing adjacent to and generally parallel to the first side of the anode and flowing toward and into the overflow region, a lesser proportion of the electrolyte being conveyed in a second stream from a second inlet at a lower flow rate, the second stream flowing adjacent to and generally parallel to the second side of the anode and flowing toward and into the overflow region;

removing the electrolyte into the overflow tank once the electrolyte has passed through the electrolysis region and the overflow region;

separating anode sludge from the electrolyte in the overflow tank; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region.

2. The process as claimed in claim 1 wherein the electrolyte is conveyed with respect to the anode such that a substantial proportion of the anode sludge formed during electrolysis is removed from the flowing electrolyte to the overflow tank.

3. The process as claimed in claim 1 wherein the temperature, conversion and contents of the electrolyte are continuously controlled during circulation of the electrolyte.

4. The process as claimed in claim 1 wherein the cathodically connected workpiece is stationary during the electrolytic surface coating.

5. The process as claimed in claim 1 wherein the cathodically connected workpiece is moved during the electrolytic surface coating thereof.

6. The process as claimed in claim 1 wherein the workpiece has a surface submerged in the electrolyte and the first stream flows generally parallel to the surface of the workpiece.

7. The process as claimed in claim 1 wherein, during circulation of the electrolyte through the overflow tank, the anode sludge is separated or precipitated from the electrolyte by means of settling.

8. The process as claimed in claim 1 wherein, during circulation of the electrolyte through the overflow tank, the anode sludge is separated from the electrolyte by means of settling and sludge particles are retained on a filter.

9. The process as claimed in claim 1 wherein the electrically conductive workpiece is a metal intaglio cylinder.

10. The process as claimed in claim 1 wherein the first stream is introduced into the electrolysis region at a high inlet pressure.

11. The process as claimed in claim 13 wherein the anode sludge is separated from the electrolyte by precipitation.

12. A process as claimed in claim 1 wherein the side of the anode closest to the workpiece and the side, of the anode farthest from the workpiece are the two largest sides of the anode.

13. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into and around an electrolysis region defined by an anode and a cathodically connected workpiece, a greater portion of the electrolyte being conveyed at a high flow rate into a space between the cathodically connected workpiece and the anode, and a lesser proportion of the electrolyte be conveyed at a lower flow rate at a side of the anode away from the workpiece, the cathodically connected workpiece being moved by rotation thereof during the electrolytic surface coating;

removing the electrolyte into a separate overflow tank once the electrolyte has passed through the electrolysis region;

separating anode sludge from the electrolyte in the overflow tank; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region.

14. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into and around an electrolysis region defined by an anode and a cathodically connected workpiece, a greater portion of the electrolyte being conveyed at a high flow rate into a space between the cathodically connected workpiece and the anode, and a lesser proportion of the electrolyte be conveyed at a lower flow rate at a side of the anode away from the workpiece;

removing the electrolyte into a separate overflow tank once the electrolyte has passed through the electrolysis region;

separating anode sludge from the electrolyte in the overflow tank; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region;

wherein anode material is continuously added.

15. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into and around an electrolysis region defined by an anode and a cathodically connected workpiece, a greater portion of the electrolyte being conveyed at a high flow rate into a space between the cathodically connected workpiece and the anode, and a lesser proportion of the electrolyte be conveyed at a lower flow rate at a side of the anode away from the workpiece;

removing the electrolyte into a separate overflow tank once the electrolyte has passed through the electrolysis region;

separating or precipitating anode sludge from the electrolyte in the overflow tank by means of electrodes; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region.

16. An apparatus for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the apparatus comprising:

means for connecting the workpiece to a cathode;

an electrolysis tank wherein release of a coating material from an anode or an electrolyte occurs and wherein at least a portion of the workpiece is positioned for surface coating so that a first side of the anode is closest to the workpiece and a second side of the anode is farthest from the workpiece, the electrolysis tank having an overflow region;

a first and second inlet means for introducing the electrolyte into an electrolysis region in the electrolysis tank, the electrolysis region being defined as a space about the workpiece and the anode, the first inlet means producing at a higher flow rate a first stream flowing adjacent to and generally parallel to the first side of the anode and flowing toward and into the overflow region, the second inlet means producing at a lower flow rate a second stream flowing adjacent to and generally parallel to the second side of the anode and flowing toward and into the overflow region;

at least one overflow tank in communication with the electrolysis tank into which the electrolyte is conveyed after flowing through the electrolysis region and the overflow region; and

a feedback device for circulating the electrolyte between the overflow tank and electrolysis tank, the feedback device including control means for controlling the amount, direction and speed of the electrolyte.

17. The apparatus as claimed in claim 16 wherein the inlet means comprises inlet lines and apertures, the inlet lines and apertures being positioned within the electrolysis tank.

18. The apparatus as claimed in claim 17 wherein the inlet lines and apertures for the electrolyte are variable in size, number, disposition and flow rate.

19. The apparatus as claimed in claim 16 wherein the feedback device includes a filter to facilitate cleaning of anode sludge.

20. An apparatus as claimed in claim 16 wherein the apparatus is adapted for submersing a surface of the workpiece in the electrolyte and the apparatus is adapted for enabling the first stream to flow generally parallel to the submerged surface of the workpiece when the workpiece is present.

21. An apparatus as claimed in claim 16 wherein the first side of the anode and the second side of the anode are the two largest sides of the anode.

22. An apparatus for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the apparatus comprising:

means for connecting the workpiece to a cathode;

an electrolysis tank wherein release of a coating material from an anode or an electrolyte occurs and wherein the surface coating of a cathodically connected workpiece occurs;

inlet means for introducing the electrolyte into an electrolysis region defined as a space about the workpiece and the anode;

at least one overflow tank in communication with the electrolysis tank into which the electrolyte is conveyed after flowing through the electrolysis region, wherein a base of the overflow tank comprises a settling cone; and

a feedback device capable of circulating the electrolyte between the overflow tank and electrolysis tank, the feedback device including a control means for controlling the amount, direction and speed of the electrolyte.

23. The apparatus as claimed in claim 22 wherein the settling cone includes baffles to improve precipitation of anode sludge.

24. The apparatus as claimed in claim 22 wherein the settling cone includes precipitation electrodes to improve the degree of precipitation.

25. The apparatus as claimed in claim 22 further comprising a filter in the flow direction upstream of a conveyance unit.

26. The apparatus as claimed in claim 22 wherein the apparatus is adapted for holding the workpiece in a fixed position in the electrolysis tank.

27. The apparatus as claimed in claim 26 wherein the apparatus is adapted for fully immersing the workpiece in the electrolyte when the electrolyte is present.

28. The apparatus as claimed in claim 26 wherein the apparatus is adapted for partially immersing the workpiece in the electrolyte when the electrolyte is present.

29. The apparatus as claimed in claim 26 wherein the anode is adapted for immersion in the electrolyte and for being optimally disposed relative to the workpiece when the workpiece is present.

30. The apparatus as claimed in claim 22 wherein the apparatus is adapted for holding the workpiece in a movable position in the electrolysis tank.

31. The apparatus as claimed in claim 30 wherein the apparatus is adapted for moving the workpiece in a rotatable manner in the electrolysis tank.

32. The apparatus as claimed in claim 22 wherein the workpiece is adapted to be a printing cylinder for intaglio printing, the apparatus being adapted for partially immersing the workpiece in the electrolyte, the anodes being dish-shaped and disposed a short distance from the printing cylinder when present, the anode sections being porous or perforated, and wherein the inlet means for the electrolyte into the electrolysis region is designed to enable precise controlled supply of electrolyte into the electrolysis region and control of the electrolyte with respect to amount, distribution, direction and speed thereof.

33. The apparatus as claimed in claim 22 further including control means for optimization of the electrolyte flow rate, temperature and concentration.

34. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into and around an electrolysis region defined by an anode and a cathodically connected workpiece, a greater portion of the electrolyte being conveyed at a high flow rate into a space between the cathodically connected workpiece and the anode, and a lesser proportion of the electrolyte be conveyed at a lower flow rate at a side of the anode away from the workpiece;

removing the electrolyte into a separate overflow tank once the electrolyte has passed through the electrolysis region, the overflow tank having a base comprising a settling cone;

separating anode sludge from the electrolyte in the overflow tank by allowing the anode sludge to settle in the settling cone; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region.

35. An apparatus for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the apparatus comprising:

means for connecting the workpiece to a cathode;

an electrolysis tank wherein release of a coating material from an anode or an electrolyte occurs, wherein the surface coating of the workpiece occurs, and wherein the apparatus is adapted for rotating the workpiece

inlet for introducing the electrolyte into an electrolysis region defined as a space about the workpiece and the anode;

at least one overflow tank in communication with the electrolysis tank into which the electrolyte is conveyed after flowing through the electrolysis region; and

a feedback device for circulating the electrolyte between the overflow tank and electrolysis tank, the feedback device including a control means for controlling the amount, direction and speed of the electrolyte.

36. A process for electrolytic surface coating of an electrically conductive workpiece by means of a fluid electrolyte, the process comprising:

conveying the electrolyte in a controlled circuit into an electrolysis tank and into and around an electrolysis region in the electrolysis tank, the electrolysis region being defined by an anode and a cathodically connected workpiece, the electrolysis tank having an overflow region through which electrolyte can flow from the electrolysis region and into an overflow tank, the anode having a first side closest to the workpiece and a second side farthest from the workpiece, the electrolyte being conveyed in a first stream from a first inlet into a space between the cathodically connected workpiece and the anode, the first stream flowing adjacent to and generally parallel to the first side of the anode and flowing toward and into the overflow region, the electrolyte being conveyed in a second stream from a second inlet, the second stream flowing adjacent to and generally parallel to the second side of the anode and flowing toward and into the overflow region;

removing the electrolyte into the overflow tank once the electrolyte has passed through the electrolysis region and the overflow region;

separating anode sludge from the electrolyte in the overflow tank; and

feeding the electrolyte back from the overflow tank into and around the electrolysis region.